We read 14 results from Mid-Peninsula Water District’s 2025 water quality report. No results over a legal limit; 3 above a health goal or guideline.
Serves about 30,609 people · Water system ID CA4110001 · Read the district’s 2025 report (opens in a new tab)
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Results from the 2025 report
Each number is copied from the district’s report and links to the page it’s printed on. Where the report lists several plants, wells or purchased water, the highest is shown.
| Contaminant | Result | Health goal | Legal limit | What it means |
|---|---|---|---|---|
| Bromatehighest running annual average · range 1.9 to 4.1 · Treated water · 2025 report, page 6 | 3.5 ppb | 0.1 ppb | 10 ppb | Above the health goal35x the health goal |
| Chromium-6average · range ND to 0.1 · Treated water · 2025 report, page 6 | 0.1 ppb | 0.02 ppb | 10 ppb | Above the health goal5x the health goal |
| Lead90th percentile of homes tested · sampled 2024 · Customer taps · 2025 report, page 7 | 3.61 ppb | 0.2 ppb | 15 ppb (action level) | Above the health goal18x the health goal |
| Chloraminehighest running annual average · range 0.55 to 3.45 · Distribution system · 2025 report, page 6 | 2.67 ppm | None set | 4 ppm | Below the legal limit |
| Chlorideaverage · range ND to 19 · Treated water · 2025 report, page 7 | 9.8 ppm | — | 250 ppm guideline | Within the guideline |
| Copper90th percentile of 33 homes tested, 0 over the action level · printed as 46 ppb · sampled 2024 · Customer taps · 2025 report, page 7 | 0.05 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (HAA5)highest running annual average · range 10.1 to 45.3 · Distribution system · 2025 report, page 6 | 34.4 ppb | None set | 60 ppb | Below the legal limit |
| Disinfection byproducts (TTHM)highest running annual average · range 21.2 to 58.6 · Distribution system · 2025 report, page 6 | 45.3 ppb | None set | 80 ppb | Below the legal limit |
| Fluorideaverage · range 0.5 to 0.8 · Treated water · 2025 report, page 7 | 0.7 ppm | 1 ppm | 2 ppm | Below the health goal |
| Ironaverage · range ND to 0.04 · printed as 12 ppb · Treated water · 2025 report, page 7 | 0.01 ppm | — | 0.3 ppm guideline | Within the guideline |
| Sulfateaverage · range 1 to 45 · Treated water · 2025 report, page 7 | 21 ppm | — | 250 ppm guideline | Within the guideline |
| Total dissolved solidsaverage · range 24 to 197 · Treated water · 2025 report, page 7 | 117 ppm | — | 500 ppm guideline | Within the guideline |
| Hardnessaverage · range 0.47 to 6.55 · Treated water · 2025 report, page 7 | 3.63 gpg (62 ppm) | — | — | Moderately hard |
| Sodiumaverage · range 3.1 to 29 · Treated water · 2025 report, page 7 | 18 ppm | None set | None | No health limit |
Utility results describe the whole system, measured where water enters the pipes, not your tap. Your home’s plumbing can add lead or copper.
What you can do
Nothing here is an emergency notice: if the district has a violation, it must tell customers directly. If you’d like to lower these at your tap, these are the treatments that remove them, and the catalog shows the models certified for each. Ranking is by certified removal; commissions never change the order.
Lead
Found: Lead
What removes it: Certified carbon block or RO.
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